Nektar Therapeutics Announces Positive 52-Week Results for Rezpegaldesleukin in Severe Alopecia Areata

New data shows continued hair growth and safety with extended treatment in Phase 2b study

Apr. 20, 2026 at 12:06pm by

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A highly detailed, translucent X-ray image showing the complex internal structure of a human hair follicle, conceptually representing the potential of a new treatment to address the underlying biology of alopecia areata.New data on a novel biologic therapy suggests it could transform the treatment of severe alopecia areata by promoting sustained hair regrowth.San Francisco Today

Nektar Therapeutics today announced new 52-week results from the Phase 2b REZOLVE-AA study evaluating investigational rezpegaldesleukin, a first-in-class IL-2 pathway agonist, in patients with severe-to-very-severe alopecia areata. The data showed that continued twice-monthly treatment led to a deepening of responses, with 29% and 31% of patients in the low and high dose extension arms, respectively, achieving a Severity of Alopecia Tool (SALT) Score of 20 or less by week 52, indicating 80% or more scalp coverage. The treatment was well-tolerated, with a favorable safety profile consistent with previous studies.

Why it matters

Alopecia areata is a devastating autoimmune condition that causes unpredictable hair loss, affecting an estimated 700,000 people in the U.S. Current therapies have high relapse rates and limited durability, so new treatment options with the potential for sustained hair regrowth are urgently needed. These positive 52-week results for rezpegaldesleukin suggest it could become a first-in-class biologic therapy to transform the management of severe alopecia areata.

The details

In the 16-week blinded treatment extension, 31 patients continued on rezpegaldesleukin at their induction dose of either 18 μg/kg or 24 μg/kg, administered subcutaneously twice-monthly. From week 36 to week 52, 29% of patients on the low dose and 31% on the high dose achieved a SALT Score of 20 or less, compared to none in the placebo arm. Overall at week 52, 25.8% of patients on low-dose and 27.6% on high-dose rezpegaldesleukin achieved this clinically meaningful hair growth threshold, versus 6.7% with placebo. Patients also showed improvements across other SALT Score measures, with the treatment well-tolerated and 94% of extension participants completing 52 weeks of dosing.

  • The REZOLVE-AA study enrolled patients from February 2025 through enrollment completion in February 2025.
  • In February 2025, the FDA granted Fast Track designation for rezpegaldesleukin for the treatment of severe alopecia areata.
  • The 52-week results announced today are from the 16-week blinded treatment extension that followed the initial 36-week induction phase of the study.

The players

Nektar Therapeutics

A clinical-stage biotechnology company focused on developing treatments for autoimmune and inflammatory diseases, and the sponsor of the REZOLVE-AA study.

Rezpegaldesleukin

Nektar's investigational first-in-class IL-2 pathway agonist and regulatory T-cell (Treg) biologic being evaluated for the treatment of severe alopecia areata.

Jonathan Silverberg, MD, PhD, MPH

Professor of Dermatology at The George Washington University School of Medicine and Health Sciences, and an investigator on the REZOLVE-AA study.

David Rosmarin, MD

Chair of the Department of Dermatology and Associate Professor of Dermatology at the Indiana University School of Medicine, and an investigator on the REZOLVE-AA study.

Howard W. Robin

President and CEO of Nektar Therapeutics.

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What they’re saying

“The new SALT≤20 responders in this set of patients treated out to 52 weeks reflect how the T regulatory cell mechanism of REZPEG can have more clinical benefit over time, a phenomenon the investigators observed in the Phase 2 study in atopic dermatitis as well.”

— Jonathan Silverberg, MD, PhD, MPH, Professor of Dermatology at The George Washington University School of Medicine and Health Sciences

“These extension treatment data to 52 weeks demonstrate the potential of rezpegaldesleukin to deliver truly meaningful clinical outcomes for patients with severe-to-very-severe alopecia areata.”

— David Rosmarin, MD, Chair of the Department of Dermatology and Associate Professor of Dermatology at the Indiana University School of Medicine

“We are excited that rezpegaldesleukin has now demonstrated great promise in two large immune-mediated disease settings as we advance into registrational trials.”

— Howard W. Robin, President and CEO of Nektar Therapeutics

What’s next

Nektar plans to submit the REZOLVE-AA results for presentation at a medical conference in 2026.

The takeaway

These positive 52-week results for rezpegaldesleukin in severe alopecia areata, including a favorable safety profile and significantly more patients achieving clinically meaningful hair growth thresholds with continued treatment, suggest this first-in-class Treg mechanism could emerge as a new standard of care for this devastating autoimmune condition.